Division of labor, where organisms specialize on roles and cooperate to survive, is a strategy employed by bacteria, slime molds, eusocial insects, and even humans. Moreover, major transitions in evolution, where formerly distinct individuals join together in a higher-level unit that functions as a single reproductive entity, also exhibit division of labor. For example, single cells join together and specialize to become a multicellular organism. A fundamental question in biology is why does division of labor evolve? While biologists are fascinated by this question, it remains challenging, if not impossible, to study with natural systems due to imperfections in the historical data and long generation times. This research involves developing a software infrastructure to investigate the evolution of division of labor.
Efficiency gains resulting from division of labor are a central component of hypotheses for why division of labor evolves within groups and why major transitions in evolution occur. To understand whether efficiency gains are sufficient to motivate these evolutionary changes, the investigators study populations of digital organisms, which are fully-functional computer programs that evolve in an open-ended manner. In contrast to experimental evolution with natural systems, digital organisms have rapid generation times, unparalleled experimental control, and automated data collection that facilitates explorations of underlying mechanisms. Using the Avida digital evolution platform as a foundation, the researchers are building an infrastructure to investigate topics surrounding the evolution of division of labor, including: (1) the role of learning in the evolution of task-based division of labor, (2) whether an increased cost of reproduction influences when fraternal major transitions occur, and (3) whether specialization capabilities motivate genetically distinct organisms to reproduce as a group.
Many groups within nature exhibit division of labor. For example, ants within colonies take on highly specific roles, such as forager, medic, or nurse, and work together to ensure the survival of the colony. Another example is the cells within your body which also have highly specific functions (such as contracting to help the heart pump) and cooperate to ensure you survive. The prevalence and importance of division of labor causes scientists to wonder why evolutionary pressures gave rise to it. Unfortunately, studying the evolution of division of labor using traditional means can be quite challenging due to imperfect information surrounding systems in which division of labor has already occurred and the tremendous amount of time it takes to study evolution in laboratory settings. To address these challenges and test hypotheses regarding the evolutionary pressures that produce division of labor, we use digital evolution. Digital evolution is an evolutionary system within a computer. We extended this system to have lower-level individuals (e.g., cells or ants) within higher-level individuals (e.g., multicellular organisms or ant colonies) evolve. This system can be used by scientists to study division of labor. We used this digital evolution platform to study several different aspects of division of labor. In one study, we examined whether task-switching costs (the amount of time it takes to change between performing one task to performing a different task) could motivate the adoption of division of labor strategies. This study provided evidence that these tasks could have an evolutionary impact. The most interesting aspect of this study is that the evolved strategy involved organisms sharing partial solutions to perform more complex tasks. The strategy was very similar to an assembly line strategy, where each worker performs one step and passes on the product to the next worker. Within another study, we examined reproductive division of labor, which occurs when some lower-level individuals reproduce and others do not. For example, some cells in your body (e.g., egg and sperm cells) can be used to form a new human, but most (e.g., liver and heart cells) cannot. From the evolutionary perspective the appearance of somatic cells (the cells that cannot reproduce) is a puzzle. We discovered evidence that this form of reproductive division of labor can be beneficial if the work being done by the cells damages their DNA. The contributions of this work are two-fold. First, we developed software infrastructure that can be used by evolutionary biologists to study questions surrounding division of labor. Second, we tested hypotheses and contributed to the understanding of the conditions that favor division of labor.